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                [Usaco2010 Jan]telephone                </h1>
                <p>时间限制：1s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：64MB</p>			</div>
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                                <h3>题目描述</h3><p>奶牛们建立了电话网络，这个网络可看作为是一棵无根树连接n(1 n 100,000)个节点，节点编号为1 .. n。每个节点可能是(电话交换机，或者电话机)。每条电话线连接两个节点。第i条电话线连接两个节点Ai和Bi(1 Ai,Bi n; Ai Bi)。
叶子节点只连接一条电话线，这些叶子节点是位于电话网中的一个电话亭。两头奶牛需要通话，信号是沿着电话网络中连接两个顶点之间最短的路径传递。每部交换机最多可容纳K (1 K 10)对牛同时通话，对于输入的无根树，求出在任何一个时间最多可同时对话奶牛的对数。
下面是6个节点的电话网络(无根树)：
     

<img border="0" src="../file/1785_0.jpg"> 

在叶子节点1,3,5和6中有四头奶牛，如果奶牛1和奶牛3，奶牛5和奶牛6通话，那么同时通话的最大数目是2(2对奶牛同时通话)。
</p><hr/><h3>输入格式</h3><p>第1行: 用空格分开的两个整数:n和k。
第2..n+1行: 第i+1行用空格分开的两个整数，Ai和Bi。

</p><hr/><h3>输出格式</h3><p>仅1行: 一个整数表示可同时对话奶牛的对数。 
</p><hr/><h3>样例输入</h3><pre>6 1
1 2
2 3
2 4
4 5
4 6

</pre><hr/><h3>样例输出</h3><pre>2
</pre><hr/><h3>提示</h3><p>没有写明提示</p><hr/><h3>题目来源</h3><p>Gold</p>
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